MAC layer bridging of network frames between isolated and external networks

ABSTRACT

An apparatus, program product and method bridge an isolated network such as a virtual network to an external network such as another virtual network or physical network by utilizing a network adapter on the other network that is assigned the same Media Access Control (MAC) address as an isolated network adapter on the isolated network.

FIELD OF THE INVENTION

The invention relates to computers and computer software, and inparticular, to bridging network traffic between isolated and externalnetworks.

BACKGROUND OF THE INVENTION

Given the continually increased reliance on computers in contemporarysociety, computer technology has had to advance on many fronts to keepup with increased demand. One particular subject of significant researchand development efforts is parallelism, i.e., the performance ofmultiple tasks in parallel.

A number of computer software and hardware technologies have beendeveloped to facilitate increased parallel processing. From a hardwarestandpoint, computers increasingly rely on multiple microprocessors toprovide increased workload capacity. Furthermore, some microprocessorshave been developed that support the ability to execute multiple threadsin parallel, effectively providing many of the same performance gainsattainable through the use of multiple microprocessors. From a softwarestandpoint, multithreaded operating systems and kernels have beendeveloped, which permit computer programs to concurrently execute inmultiple threads so that multiple tasks can essentially be performed atthe same time.

In addition, some computers implement the concept of logicalpartitioning, where a single physical computer is permitted to operateessentially like multiple and independent “virtual” computers (referredto as logical partitions), with the various resources in the physicalcomputer (e.g., processors, memory, input/output devices) allocatedamong the various logical partitions. Each logical partition executes aseparate operating system, and from the perspective of users and of thesoftware applications executing on the logical partition, operates as afully independent computer.

Some logically-partitioned computers, as well as somenon-logically-partitioned computers, may additionally support the use ofintegrated computers. For example, some computers may support the use ofintegrated card-based computers, where complete computers, including allnecessary processors, memory and support circuitry, are mounted on cardsthat are in turn mounted in slots in a logically-partitioned computer.Each card-based computer runs its own operating system, and in mostrespects operates as a separate computer. However, typically someresources used by a card-based computer, such as mass storage andnetwork connections, are shared with and managed by thelogically-partitioned computer.

In a logically-partitioned computer, integrated card-based computers aretreated as system resources, and are typically allocated to differentlogical partitions, such that overall management and interaction withthe card-based computers are handled by the logical partitions to whichsuch card-based computers are allocated. The logical partitions alsoserve to manage mass storage and network connectivity for card-basedcomputers in such a manner that the card-based computers are able tobehave as if those computers were independent and stand-alone computers.In this manner, a large number of independently-acting card-basedcomputers may be supported and managed by a single logically-partitionedcomputer.

Considering that card-based computers are permitted to behave likeindependent computers, and that logical partitions are also permitted tobehave like independent computers, enabling these various computers tocommunicate with one another without the need for specializedfunctionality is highly desirable. Put another way, it is desirable toenable a card-based computer to communicate with a logical partition oranother card-based computer, in the same manner as that card-basedcomputer would communicate with any other independent computer. It isalso desirable to permit a logical partition to communicate with otherlogical partitions or card-based computers in the same manner as thatlogical partition would communicate with any other independent computer.

To serve these needs, the concept of “virtual networking” has beendeveloped. In a virtual network, a physical network is simulated inlower levels of software to enable higher levels of software tocommunicate in the same manner as would be required to communicate overa physical network.

For example, in an Ethernet-compatible network, connectivity issupported through the use of network adapters that are connected to aphysical medium such as a series of wires, routers, hubs, switches, etc.The network adapters are typically implemented as cards that install inavailable slots in a computer. Each network adapter typically has anidentifier that uniquely identifies the network adapter on the network,so that data can be sent to particular network adapters using theirunique identifiers. For example, each network adapter may have a uniqueMedia Access Control (MAC) address that uniquely identifies thatadapter. Network information is then typically sent over a network inthe form of frames, with those frames including the MAC addresses ofboth the source and destination network adapters. Logic in the networkadapters, as well as in any hardware components in the network itself(e.g., routers, switches, etc.), enables network frames to ultimatelyreach the destination network adapter regardless of the actual topologyof the network. As such, the computers that utilize such networkadapters are able to send information over a network without regard forwhere other network adapters, and their respective computers, reside onthe network.

Another aspect of Ethernet-based networking is the use of multiplelayers of protocols to enable higher-level networking functionality. Forexample, many networks support the use of higher-level protocols such asTCP/IP to add functionality such as guaranteed delivery, dynamicaddressing, delivery confirmation, etc. A TCP/IP packet, in essence,provides a header that “wraps” around a lower-level frame, e.g., a layer2 frame that relies on MAC addressing. Higher level protocols such asTCP/IP, however, require additional software support in the computerscoupled to a network to provide the additional functionality supportedby the protocol.

From the perspective of a computer that utilizes a network adapter toconnect to a physical network, program code resident in the computer,typically referred to as a “device driver”, is used to effectivelymanage the interaction between the computer and its network adapter,including the transfer of data to and from the network. A device driveris typically designed for a specific make and model of network adapter,and enables the operating system of a computer to be designed togenerically communicate with a network irrespective of the type ofnetwork adapter that is installed.

Virtual networking relies on many of the same protocols as physicalnetworking, such that the operating system and device drivers in acomputer that communicate with a virtual network are able to do so inthe same manner that would occur were a physical network used. Insteadof using physical network adapters, however, virtual networking relieson the use of “virtual” network adapters that effectively mimic theoperations of a physical network adapter. The virtual network adaptersare implemented in software, and logically reside outside of the scopeof a computer attempting to communicate over a virtual network. As such,the fact that a network is virtual is effectively hidden from thecomputer.

Thus, for a card-based computer being managed by a logical partition,the virtual network adapter for the card-based computer is typicallysoftware that logically resides in a logical partition. Likewise, for alogical partition, the virtual network adapter therefor is typicallyimplemented as software resident in a partition manager.

The software-based virtual network adapters in a virtual network arelogically connected to one another to mimic the transfer of networkframes over a network. This additional functionality is also typicallyimplemented in software residing in the same logical entity as thevirtual network adapters.

As with physical networking, it may be desirable in some circumstancesto enable a virtual network adapter on a virtual network to communicatewith network adapters on other networks. For example, in theaforementioned logically-partitioned computer architecture that utilizesintegrated card-based computers, it may be desirable to permit anintegrated card-based computer being managed by one logical partition tocommunicate with an integrated card-based computer being managed byanother logical partition, or to communicate with another computer thatis physically remote from the logically-partitioned computer (as acard-based computer may not have its own hardware-based network port).Given, however, that the virtual networks for the integrated card-basedcomputers reside within the logical partitions, direct connectivity bycomputers that are not logically located in the same logical partitionis prohibited. In this regard, the virtual networks implemented within alogical partition or within a partition manager are effectively“isolated” networks insofar as no direct communication is supported withexternal networks.

Thus, a significant need exists for a manner of “bridging” an isolatednetwork such as a virtual network with another network (virtual orphysical) that is external to the computer within which the virtualnetwork is implemented.

Traditional bridging mechanisms used for bridging physical networks havenot been found to be optimal for isolated or virtual networkapplications. For example, some physical networks rely on hardwarenetwork switches or routers to bridge network traffic between multiplenetworks. However, given that virtual networks are implemented entirelyin software, the use of hardware switches and the like is not feasible.As another example, some physical networks rely on software-implementednetwork bridges to bridge traffic between network adapters coupled todifferent networks. Conventional software-implemented network bridges,however, typically rely on TCP/IP or other higher level protocols toimplement bridging, which is relatively complex to implement, requiresadditional processing overhead, requires operating system participation,and limits bridging to data communicated only using specific higherlevel protocols.

Therefore, a significant need continues to exist in the art for a mannerof bridging network traffic between an isolated network such as avirtual network, and other virtual and/or physical networks.

SUMMARY OF THE INVENTION

The invention addresses these and other problems associated with theprior art in providing an apparatus, program product and method in whichan isolated network such as a virtual network is bridged to anothervirtual network or physical network by utilizing a network adapter onthe other network that is assigned the same Media Access Control (MAC)address as a network adapter on the isolated network (hereinafterreferred to as an isolated network adapter). By duplicating the MACaddress on the two network adapters, bridging is effectively implementedat a lower network layer (e.g., layer 2) than that used in higher levelbridging algorithms such as TCP/IP-based bridging.

Consistent with the invention, outbound network traffic transmitted byan isolated network adapter on an isolated network is bridged to anothernetwork by detecting the transmission of a network frame on the isolatednetwork that has a source MAC address associated therewith that matchesthat of the isolated network adapter on the isolated network. Upon suchdetection, the network frame is then forwarded to the other networkusing another network adapter on the other network and having the sameMAC address such that the source MAC address for the network frameeffectively identifies the isolated network adapter as the source of thenetwork frame. As such, from the perspective of a destination networkadapter the isolated network adapter is considered the originator of thenetwork frame.

Also consistent with the invention, inbound network traffic transmittedover another network to an isolated network adapter resident on anisolated network is bridged to the isolated network by simply forwardingnetwork frames having a destination MAC address matching that of theisolated network adapter once received by another network adapter on theother network that has the same MAC address as the isolated networkadapter.

These and other advantages and features, which characterize theinvention, are set forth in the claims annexed hereto and forming afurther part hereof. However, for a better understanding of theinvention, and of the advantages and objectives attained through itsuse, reference should be made to the Drawings, and to the accompanyingdescriptive matter, in which there is described exemplary embodiments ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary computer architecturesupporting MAC layer network bridging for a virtual isolated network ina manner consistent with the invention.

FIG. 2 is a block diagram of another exemplary computer architecturesupporting MAC layer network bridging for a physical isolated network ina manner consistent with the invention.

FIG. 3 is a flowchart illustrating the sequence of operations duringtransmission of outbound data from an isolated network adapter in eitherof the computer architectures of FIGS. 1 and 2.

FIG. 4 is a flowchart illustrating the sequence of operations duringtransmission of inbound data to an isolated network adapter in either ofthe computer architectures of FIGS. 1 and 2.

FIG. 5 is a block diagram of the principal hardware components in alogically-partitioned computer implementing MAC layer network bridgingconsistent with the invention.

FIG. 6 is a block diagram of the principal components involved incommunicating data between two integrated computers in separate logicalpartitions of the logically-partitioned computer of FIG. 5.

FIG. 7 is a block diagram of the principal components involved incommunicating data between an integrated computer and a physical networkin the logically-partitioned computer of FIG. 5.

DETAILED DESCRIPTION

The embodiments discussed hereinafter bridge an isolated network such asa virtual network to an external network, such as another virtualnetwork or physical network, by utilizing a network adapter on the othernetwork that is assigned the same Media Access Control (MAC) address asan isolated network adapter on the isolated network.

To implement MAC layer bridging as described hereinafter, a computercoupled to an isolated network, and having a network adapter with aknown MAC address, is coupled to an external network via an intermediatecomputer. The intermediate computer has the ability to see all trafficon the isolated network being sent by the isolated computer using anadapter having the known MAC address, as well as the ability to sendframes to the isolated network with the appearance of coming from anysource MAC address. In addition, the intermediate computer has a networkadapter coupled to the external network and configured to use the sameMAC address as the known MAC address of the isolated network adapter.Since these adapters are on separate networks, no duplicate MACaddresses will be seen.

When the intermediate computer sees that a frame has been sent from theknown source MAC address on the isolated network, the intermediatecomputer is configured to send an identical frame to the externalnetwork using its network adapter that is configured to use the samesource MAC address. Likewise, when the intermediate computer receives aframe from the external network that is addressed to the known MACaddress, the intermediate computer will send an identical frame to theisolated network to be received by the isolated network adapter.

As will become more apparent below, one manner in which an intermediatecomputer can relay frames between an isolated network and an externalnetwork is through the use of cooperative network adapters and devicedrivers that are respectively coupled to the isolated and externalnetworks. Specifically, the device drivers for the network adapterscoupled to each of the isolated and external networks may be configuredto pass MAC layer traffic to one another to ensure that outbound andinbound data frames emanating from, and directed to, the isolatednetwork adapter are passed to and from the external network. However, itwill be apparent to one of ordinary skill in the art having the benefitof the instant disclosure that in lieu of an intermediate networkadapter and cooperative device drivers, other manners of communicatingdata between a network adapter on an isolated network and a networkadapter on an external network may be used to implement MAC layerbridging consistent with the invention.

Turning now to the Drawings, wherein like numbers denote like partsthroughout the several views, FIG. 1 illustrates an exemplary computerarchitecture 10 wherein a first computer 12 (also designated “computerA”) is shown resident within a second computer 14 (also designated“computer B”). Computer 14 is coupled to an external network 16, whereascomputer 12 is logically coupled to computer 14 via an isolated network18.

Network 18 is isolated from the standpoint that the network is notdirectly coupled to external network 16. As will become more apparentbelow, either of networks 16, 18 may be implemented as a physicalnetwork or as a virtual network. In the implementation of FIG. 1, forexample, isolated network 18 is implemented as a virtual networkresident in computer 14. In this implementation, in particular, computer12 is logically managed by computer 14, typically where computer 12 iseither an integrated computer installed into computer 14, or wherecomputer 12 is a logical partition or other form of “virtual computer”that is executing on the hardware of computer 14.

To implement MAC layer bridging consistent with the invention,architecture 10 relies on a set of network adapters 20, 22 and 24, eachmanaged by an associated device driver 26, 28 and 30, and each having astored MAC address 32, 34 and 36. In particular, computer 12communicates with network 18 through the use of a device driver 26 thatis logically coupled to an isolated network adapter 20 (also designatedas “adapter A”) that is in turn logically coupled to network 18. Asrepresented by the inclusion of device driver 26 within the boxdesignating computer 12 in FIG. 1, device driver 26 is within the“scope” of computer 12. Likewise, the exclusion of network adapter 20from the box designating computer 12 represents the fact that theadapter is outside of the scope of computer 12, and thus the fact thatthe adapter may be a virtual adapter is effectively hidden from computer12.

Also coupled to network 18 is another network adapter 22 (alsodesignated as “adapter B”), which is managed by a device driver 28 thatis resident in computer 14. Computer 14 then communicates with network16 via a network adapter 24 (also designated as “adapter C”) that ismanaged by a device driver 30. Device drivers 28 and 30 are bothresident in computer 14, and as such, may communicate with one anotherin the scope of computer 14.

MAC layer bridging consistent with the invention is implemented inarchitecture 10 specifically through the interaction of device drivers28, 30 in passing frames of data between networks 16 and 18, which inthe illustrated embodiments occurs in the form of layer 2 (MAC layer)traffic. It will be appreciated that data transmitted over a network istypically partitioned into data elements often referred to as “packets”or “frames,” depending on the particular protocol used. As such, theterm “frame” will hereinafter be used to refer to any type of dataelement communicated over a network, including a packet.

In addition, network adapters 20, 24 are assigned the same source MACaddress (designated here as “MAC1”) such that outbound frames generatedby network adapter 20 (and thus having source MAC addresses of MAC1)will be relayed to adapter 24 and output to network 16 using the samesource MAC address of MAC1. Likewise, inbound data frames having adestination MAC address of MAC1will be recognized by adapter 24 andautomatically forwarded to network 18 via the interaction of devicedrivers 28, 30.

An alternate implementation of a computer architecture suitable forutilizing MAC layer bridging consistent with the invention isillustrated at 50 in FIG. 2. Here, a first computer 52 (“computer A”) isphysically separate from a second computer 54 (“computer B”). Computer52 is isolated from an external network 56, being coupled to computer 54via an isolated network 58. Given computer 52 is separate from computer54, however, network 58 is typically a physical network, rather than avirtual network as with computer architecture 10 of FIG. 1.

To interface computer 52 with external network 56, a series of networkadapters 60 (“adapter A”), 62 (“adapter B”) and 64 (“adapter C”) areused, with each managed by a respective device driver 66, 68 and 70, andeach having a respective MAC address 72, 74 and 76. Also, as above witharchitecture 10, adapters 60 and 64, respectively coupled to isolatedand external networks 58, 56, are assigned the same MAC address(designated here as “MAC1”). In addition, device drivers 68, 70 areconfigured to pass layer 2 or MAC layer traffic to one another toeffectively relay appropriate data frames between networks 56, 58 in amanner consistent with the invention.

The specific manner in which frames are bridged between isolated andexternal networks in architectures 10 and 50 is further illustrated bythe flowcharts illustrated in FIGS. 3 and 4.

FIG. 3, in particular, illustrates at 80 the outbound data flow thatoccurs whenever computer A (computer 12 or 52 of FIGS. 1, 2) attempts tosend a packet to an external network 16, 56. Starting in block 82, theadapter A device driver receives a frame from the network stack of theoperating system for computer A (designated “OS A”) and transmits theframe using adapter A. Next, as shown in block 83, adapter A receivesthe frame and passes the frame to the virtual network using the adapterA MAC address as the source address for the frame.

Next, as shown in block 84, adapter B receives the frame and passes theframe to the adapter B device driver. Thereafter, as shown in block 85,the adapter B device driver detects the adapter A MAC address as thesource address of the transmitted frame, and, in response to suchdetection, passes the frame to the adapter C device driver unchanged(i.e., with the source MAC address still specifying adapter A as thesource of the packet).

Next, as shown in block 86, the adapter C device driver receives theframe and transmits the frame using adapter C. As shown in block 88,adapter C then transmits the frame to the external network using theadapter C MAC address as the source address for the frame. Given, thatthe adapter C MAC address is the same as the adapter A MAC address,however, it appears from the perspective of another network adaptercoupled to the external network, that adapter A is the source of thetransmitted frame.

Likewise, FIG. 4 illustrates at 90 the inbound data flow that occurswhen a network adapter coupled to an external network attempts tocommunicate data to computer A via network adapter A. As shown at block92, a frame communicated to an external network is received by adapter C(as the adapter is configured with the same MAC address as adapter A)and passed to the adapter C device driver. Next, as shown in block 93,the adapter C device driver receives the frame, and automatically passesthe frame to the adapter B device driver. Next, as shown in block 94,the adapter B device driver receives the frame and transmits the frameusing adapter B, whereby as shown in block 95, the adapter B receivesthe frame and transmits such over the virtual network unchanged (i.e.,using the same source MAC address as was provided in the originalframe).

Next, as shown in block 96, adapter A receives the frame over theisolated network, and passes the frame to the adapter A device driver.Thereafter, as shown in block 98, the adapter A device driver receivesthe frame from adapter A, whereby reception of the frame by computer Ais complete.

It will be appreciated therefore that the passing of frames between anisolated network and an external network is implemented at least in partthrough the interaction of the device drivers for adapters B and C.Where computer B represents a logical partition in alogically-partitioned computer, for example, the device drivers areresident in the partition operating system. Where computer B is aseparate computer from computer A, the device drivers are likewiseimplemented within a common operating system. It will be appreciatedthat configuration of each device driver to implement theherein-described functionality would be well within the ability of oneof ordinary skill in the art having the benefit of the instantdisclosure.

It should also be noted that, in some embodiments, the invention may beimplemented simply via the aforementioned device drivers, along withsetting the MAC addresses for adapters A and C to the same value.Otherwise all other software and hardware components may be conventionalin nature.

It will also be appreciated that an isolated network may be implementedusing any network that is logically isolated from (and thus not directlycoupled to) an external network, and that an isolated network may bephysical or virtual in nature. Moreover, it will be appreciated that anexternal network may be practically any type of network, whetherphysical or virtual in nature. Therefore, the invention is not limitedto the particular implementations discussed herein.

As noted above, the aforementioned technique for bridging an isolatednetwork to an external network may be used in a wide variety ofapplications. One specific application, which is described in greaterdetail below in connection with FIGS. 5-7, is that of bridging networktraffic from an integrated card-based computer in alogically-partitioned computer such as computer 110 of FIG. 5.

Computer 110, in particular, generically represents, for example, any ofa number of multi-user computers such as a network server, a midrangecomputer, a mainframe computer, etc., e.g., an IBM eServer iSeriescomputer. However, it should be appreciated that the invention may beimplemented in other computers and data processing systems, e.g., insingle-user computers such as workstations, desktop computers, portablecomputers, and the like, or in other programmable electronic devices(e.g., incorporating embedded controllers and the like). In addition,the invention may also be utilized in connection with non-logicallypartitioned multithreaded computers.

As best shown in FIG. 5, computer 110 generally includes one or moreprocessors 112 coupled to a memory 114 via a bus 116. Each processor 112may be implemented as a single threaded processor, or as a multithreadedprocessor, such as with processor 112 a, which is shown incorporating aplurality of hardware threads 118. For the most part, each hardwarethread 118 in a multithreaded processor 112 a is treated like anindependent processor by the software resident in the computer. In thisregard, for the purposes of this disclosure, a single threaded processorwill be considered to incorporate a single hardware thread, i.e., asingle independent unit of execution. It will be appreciated, however,that software-based multithreading or multitasking may be used inconnection with both single threaded and multithreaded processors tofurther support the parallel performance of multiple tasks in thecomputer.

In addition, as is also illustrated in FIG. 5, one or more of processors112 (e.g., processor 112 b) may be implemented as a service processor,which is used to run specialized firmware code to manage system initialprogram loads (IPLs), and to monitor, diagnose and configure systemhardware. Generally, computer 110 will include one service processor andmultiple system processors, which are used to execute the operatingsystems and applications resident in the computer, although theinvention is not limited to this particular implementation. In someimplementations, a service processor may be coupled to the various otherhardware components in the computer in manner other than through bus116.

Memory 114 may include one or more levels of memory devices, e.g., aDRAM-based main storage, as well as one or more levels of data,instruction and/or combination caches, with certain caches eitherserving individual processors or multiple processors as is well known inthe art. Furthermore, memory 114 is coupled to a number of types ofexternal devices via a bus 120, e.g., one or more physical networkadapters 122 (for interfacing the computer with external network(s)124), one or more storage controllers 126 (for interfacing the computerwith one or more storage devices 128) and one or more workstationcontrollers 130 (for interfacing with one or more terminals orworkstations 132 via a plurality of workstation adapters).

An additional type of external device that may be coupled to bus 120 isone or more integrated computers 133, e.g., integrated card-basedcomputers such as Integrated xSeries servers available from IBM. As isknown in the art, an Integrated xSeries server provides an Intel-basedserver on a PCI card and running a version of a Microsoft Windowsoperating system, which is capable of being plugged into a PCI slot inan IBM iSeries server to leverage the iSeries server's systemmanagement, communication and storage resources, while otherwiseoperating as a standalone Windows-based server. Other forms ofintegrated computers, whether or not card-based, may be used consistentwith the invention.

FIG. 5 also illustrates in greater detail the primary softwarecomponents and resources utilized in implementing a logicallypartitioned computing environment on computer 110, including a pluralityof logical partitions 134 managed by a partition manager or hypervisor136. Any number of logical partitions may be supported as is well knownin the art, and the number of logical partitions resident at any time ina computer may change dynamically as partitions are added or removedfrom the computer.

In the illustrated IBM eServer-based implementation, partition manager136 is comprised of two layers of program code. The first, referred toherein as a non-dispatchable portion 138, is implemented within thefirmware, or licensed internal code (LIC), of computer 110, which isutilized to provide a low level interface to various hardware componentswhile isolating higher layers, e.g., the operating systems, from thedetails of the hardware access. The firmware may also communicate with aservice processor such as service processor 112 b. The non-dispatchableportion 138 provides many of the low level partition managementfunctions for computer 110, e.g., page table management, etc. Thenon-dispatchable portion 138 also has no concept of tasks, and isaccessible principally via function calls from higher layers ofsoftware.

The second layer of program code in partition manager 136 is referred toherein as a dispatchable portion 140. In contrast to non-dispatchableportion 138, which has no concept of tasks, is run with relocation off,and is accessible via function calls from higher layers of software, thedispatchable portion 140 has the concept of tasks (like any operatingsystem), and is run with relocation on. The dispatchable portiontypically executes in much the same manner as a partition, except thatit is hidden from the user. The dispatchable portion generally manageshigher level partition management operations such as creating anddeleting partitions, concurrent I/O maintenance, allocating processors,memory and other hardware resources to various partitions 134, etc.

Each logical partition 134 is typically statically and/or dynamicallyallocated a portion of the available resources in computer 110. Forexample, each logical partition may be allocated one or more processors112 and/or one or more hardware threads 118, as well as a portion of theavailable memory space. Logical partitions can share specific hardwareresources such as processors, such that a given processor is utilized bymore than one logical partition. In the alternative hardware resourcescan be allocated to only one logical partition at a time.

Additional resources, e.g., mass storage, backup storage, user input,network connections, integrated computers, and the I/O adapterstherefor, are typically allocated to one or more logical partitions in amanner well known in the art. Resources may be allocated in a number ofmanners, e.g., on a bus-by-bus basis, or on a resource-by-resourcebasis, with multiple logical partitions sharing resources on the samebus. Some resources may even be allocated to multiple logical partitionsat a time.

Each logical partition 134 utilizes an operating system 142 thatcontrols the primary operations of the logical partition in the samemanner as the operating system of a non-partitioned computer. Forexample, each operating system 142 may be implemented using the OS/400operating system available from International Business MachinesCorporation.

Each logical partition 134 executes in a separate, or independent,memory space, and thus each logical partition acts much the same as anindependent, non-partitioned computer from the perspective of each userapplication (user app) 144 that executes in each such logical partition.As such, user applications typically do not require any specialconfiguration for use in a partitioned environment.

Given the nature of logical partitions 134 as separate virtualcomputers, it may be desirable to support inter-partition communicationto permit the logical partitions to communicate with one another as ifthe logical partitions were on separate physical machines. As such, insome implementations it may be desirable to support a virtual local areanetwork (LAN) 146 in non-dispatchable portion 138 to permit logicalpartitions 134 to communicate with one another via a networking protocolsuch as the Ethernet protocol. Other manners of supporting communicationbetween partitions may also be supported consistent with the invention.Moreover, as will become more apparent below, within each logicalpartition 134 may be supported a virtual network (not shown in FIG. 5)to allow integrated computers resident in a given logical partition tocommunicate with one another.

It will be appreciated that other logically-partitioned environments maybe utilized consistent with the invention. For example, rather thanutilizing a dispatchable portion 140 that is separate from any partition134, the functionality of the dispatchable portion may be incorporatedinto one or more logical partitions in the alternative.

In general, the routines executed to implement the embodiments of theinvention, whether implemented as part of an operating system or aspecific application, component, program, object, module or sequence ofinstructions, or even a subset thereof, will be referred to herein as“computer program code,” or simply “program code.” Program codetypically comprises one or more instructions that are resident atvarious times in various memory and storage devices in a computer, andthat, when read and executed by one or more processors in a computer,cause that computer to perform the steps necessary to execute steps orelements embodying the various aspects of the invention. Moreover, whilethe invention has and hereinafter will be described in the context offully functioning computers and computer systems, those skilled in theart will appreciate that the various embodiments of the invention arecapable of being distributed as a program product in a variety of forms,and that the invention applies equally regardless of the particular typeof signal bearing media used to actually carry out the distribution.Examples of signal bearing media include but are not limited torecordable type media such as volatile and non-volatile memory devices,floppy and other removable disks, hard disk drives, magnetic tape,optical disks (e.g., CD-ROMs, DVDs, etc.), among others, andtransmission type media such as digital and analog communication links.

In addition, various program code described hereinafter may beidentified based upon the application or software component within whichit is implemented in a specific embodiment of the invention. However, itshould be appreciated that any particular program nomenclature thatfollows is used merely for convenience, and thus the invention shouldnot be limited to use solely in any specific application identifiedand/or implied by such nomenclature. Furthermore, given the typicallyendless number of manners in which computer programs may be organizedinto routines, procedures, methods, modules, objects, and the like, aswell as the various manners in which program functionality may beallocated among various software layers that are resident within atypical computer (e.g., operating systems, libraries, APIs,applications, applets, etc.), it should be appreciated that theinvention is not limited to the specific organization and allocation ofprogram functionality described herein.

Those skilled in the art will recognize that the exemplary environmentillustrated in FIG. 5 is not intended to limit the present invention.Indeed, those skilled in the art will recognize that other alternativehardware and/or software environments may be used without departing fromthe scope of the invention.

FIG. 6 next illustrates the principal components involved incommunicating data between two integrated computers in separate logicalpartitions of the logically-partitioned computer of FIG. 5. Inparticular, FIG. 6 illustrates at 150 a pair of logical partitions 152,154 coupled by a virtual Ethernet network 156. Within each logicalpartition 152, 154 is a plurality of server cards (integrated computers)158 logically coupled to one another via a virtual Ethernet network 160.Each virtual network 160 represents an intra-partition network, whilevirtual network 156 represents an inter-partition network.

To maintain logical independence of partitions, it is desirable toprohibit a server card 158 in one partition from communicating directlywith a server card resident in another logical partition. In thisconfiguration, therefore, network 156 is an external network withrespect to the logical partition, while each virtual network 160 is anisolated network.

To couple each server card 158 to virtual network 160, each server cardutilizes a device driver/virtual network adapter pair. For example, forlogical partition 152, a pair of server cards A and B are shown, withserver card A having a device driver DD1 and virtual network adapterVA1, and server card having a device driver DD2 and virtual networkadapter VA2. Consistent with the invention, communication between eitherof server cards A and B, and another server card located in anotherlogical partition, is implemented by incorporating into logicalpartition 152 a pair of virtual network adapters VA1′, VA2′ coupled tovirtual network 156, and sharing the same MAC address as virtual networkadapters VA1 and VA2. In addition, to bridge network traffic betweennetworks 156 and 160, additional virtual network adapters VA3 and VA4are coupled to network 160, and respectively associated with networkadapters VA1 and VA2. Network adapters VA1′ and VA3, and networkadapters VA2′ and VA4, are logically coupled to one another viainteraction of corresponding device drivers DD1′ and DD3, and DD2′ andDD4. The logical connections are represented at 162. In addition, asillustrated in FIG. 6, the logical partition 152 may itself have avirtual port to network 156, via a network adapter VAS managed by deviceDD5.

Likewise, for logical partition 154, a pair of server cards C and D areillustrated, each including a virtual network adapter VA6, VA7 managedby a respective device driver DD6, DD7. Associated with such networkadapters are a pair of virtual network adapters VA8 and VA9, managed viadevice drivers DD8 and DD9 and coupled to network 160. Logical pathways162 couple these latter device drivers to a pair of device drivers DD6′and DD7′, which manage a pair of virtual network adapters VA6′ and VA7′,coupled to network 156. In addition, logical partition 154 may include adedicated network adapter VA10 coupled to virtual network 156 andmanaged by device driver DD10. As with logical partition 152, virtualnetwork adapters VA6′ and VA7′ of logical partition 154 have the sameMAC address as virtual network adapters VA6 and VA7.

To communicate, for example, between server card A in logical partition152 and server card D in logical partition 154, server card A, viadevice driver DD1, sends a network frame to virtual network 160 usingvirtual network adapter VA1. The network frame uses the MAC address ofadapter VA1 as the source address, and the MAC address of adapter VA7 asthe destination address. The transmission of this network frame isdetected by virtual network adapter VA3, whereupon device driver DD3relays the frame to device driver DD1′, resulting in the transmission ofthe network frame to virtual network 156 via adapter VA1′. Moreover, byvirtue of the same MAC address for network adapters VA1 and VA1′, thetransmitted frame will have a source MAC address that matches that ofnetwork adapter VA1.

In addition, it is assumed that, with server card A intending tocommunicate to server card D, the destination MAC address for thenetwork frame will be the MAC address associated with virtual networkadapter VA7. As such, virtual network adapter VA7′, having the same MACaddress, will detect the transmission of the frame on network 156, andpass the frame to device driver DD7′, which will then forward thenetwork frame to device driver DD9. Thereafter, the network frame isforwarded to network 160 via virtual network adapter VA9, with thedestination MAC address for the frame being that of virtual networkadapter VA7. As such, the frame will be received by virtual networkadapter VA7 and passed to device driver DD7 for processing by servercard D.

FIG. 6 therefore illustrates the transmission of a network frame betweenintegrated computers resident in different logical partitions via theuse of intra-partition and inter-partition networks, each of which beingvirtual in nature. In some implementations, however, it may be desirableto alternatively or additionally interface an integrated computer with aphysical network.

For example, as illustrated at 180 of FIG. 7, a logical partition 182may be coupled to a physical Ethernet network 186, and may have residenttherein a plurality of server cards 188 coupled to an isolated virtualEthernet network 190. To support bridging to network 186, each servercard may be associated with three device driver/network adapter pairs,as in FIG. 6. For example, for server cards E and F illustrated in FIG.7, each may have associated therewith a virtual network adapter VA11,VA12, with a matched device driver DD11, DD12, and coupled to virtualnetwork 190. In turn, an additional network adapter VA13, VA14 may becoupled to network 190, with a matched device driver DD13, DD14 coupledvia pathway 192 to a device driver DD11′, DD12′, used to manage aphysical network adapter PA11′, PA12′, coupled to physical network 186.In addition, the partition 182 may include a dedicated physical adapterPA15 managed by device driver DD15 to handle partition-relatedcommunications over the network 186.

The configuration of FIG. 7 may be utilized, for example, when servercards 188 are not provided with dedicated Ethernet ports, but mustotherwise rely on a logically-partitioned computer within which suchserver cards are installed, to provide external network connectivity.Communication between a server card and a network adapter coupled tonetwork 186 proceeds in much the same manner as described above. Forexample, to communicate a network frame from server card E, devicedriver DD11 utilizes virtual network adapter VA11 to communicate thenetwork frame to virtual network 190, with the source MAC address beingthat of virtual network adapter VA11, and the destination MAC addressbeing that of a network adapter coupled to network 186. Transmission ofthe frame on network 190 is detected by virtual network adapter VA13,resulting in the transmission of the frame to physical network adapterPA11′via the cooperation of device drivers DD13 and DD11′ communicatingover pathway 192. Physical network adapter PA11′ is configured to havethe same MAC address as virtual network adapter VA11, resulting in thenetwork frame output on network 186 having a source MAC address matchingthat of virtual network adapter VA11.

Likewise, for communications to server card E, a network frame having adestination MAC address matching that of both physical network adapterPA11′ and virtual network adapter VA11 is transmitted over network 186.Via the cooperation of device drivers DD11′ and DD13, the frame, oncereceived by physical network adapter PA11′ is communicated by virtualnetwork adapter VA13 over network 190. The frame, once communicated overnetwork 190, and as a result of having a destination MAC addressmatching that of virtual network adapter VA11, will be received by suchnetwork adapter and passed to device driver DD11 for handling by servercard E.

Various modifications to the herein-described embodiments will beapparent to one of ordinary skill in the art having the benefit of theinstant disclosure. Therefore, the invention lies in the claimshereinafter appended.

1. A method of interconnecting first and second integrated computersrespectively resident in first and second logical partitions in alogically-partitioned computer system, the method comprising: in a firstdevice driver resident in the first integrated computer, initiatingtransfer of a network frame over a first virtual network in the firstlogical partition using a first virtual network adapter coupled to thefirst virtual network, wherein the network frame has a source mediaaccess control (MAC) address identifying a first MAC address associatedwith the first virtual network adapter, and a destination MAC addressidentifying a second MAC address; in a second device driver for a secondvirtual network adapter coupled to the first virtual network, detectingthat the network frame communicated to the first virtual network is fromthe first virtual network adapter by detecting the first MAC address inthe network frame, and in response thereto, forwarding the network frameto a third device driver for a third network adapter coupled to aninter-partition network; in the third device driver, initiating transferof the network frame over the inter-partition network using the thirdnetwork adapter and using the first MAC address as the source MACaddress for the network frame; in a fourth device driver for a fourthnetwork adapter coupled to the inter-partition network, detecting thatthe network frame communicated to the inter-partition network isaddressed to a sixth virtual network adapter coupled to a second virtualnetwork in the second logical partition and associated with the secondMAC address, and in response thereto, forwarding the network frame to afifth device driver for a fifth virtual network adapter coupled to thesecond virtual network; in the fifth device driver, initiating transferof the network frame over the second virtual network using the fifthnetwork adapter; and receiving the network frame with the sixth networkadapter and passing the network frame to a sixth device driver residentin the second integrated computer.
 2. A method of bridging first andsecond networks, the first network coupled to a first computer via afirst network adapter in the first computer, and the second networkcoupled to a second computer via a second network adapter in the secondcomputer, and wherein the first network is an isolated network and thefirst network adapter is an isolated network adapter, the methodcomprising, in the second computer: detecting a first network framecommunicated by the first computer over the first network by detecting amedia access control (MAC) address for the first network frame that isassociated with the first network adapter; forwarding the first networkframe to the second network using the second network adapter such that asource MAC address for the first network frame identifies the firstnetwork adapter as a source of the first network frame; receiving asecond network frame from the second network via the second networkadapter, wherein the second network frame is addressed to the MACaddress associated with the first network adapter; and forwarding thesecond network frame to the first network; wherein detecting the firstnetwork frame is performed by a device driver for a third networkadapter coupled to the first network, and wherein forwarding the firstnetwork frame to the second network comprises passing the first networkframe from the device driver for the third network adapter to a devicedriver for the second network adapter, and transmitting the firstnetwork frame to the second network using the third network adapter. 3.The method of claim 2, wherein the first network is a virtual networkand the first network adapter is a virtual network adapter.
 4. Themethod of claim 3, wherein the second network is a virtual network andthe second network adapter is a virtual network adapter.
 5. The methodof claim 4, wherein the second computer comprises a logical partition ina logically-partitioned computer system, wherein the first networkcomprises an intra-partition network resident in the logical partition,and wherein the second network comprises an inter-partition networkcoupled to a plurality of logical partitions.
 6. The method of claim 3,wherein the second network is a physical network and the second networkadapter is a physical network adapter.
 7. The method of claim 3, whereinthe first computer is integrated into the second computer.
 8. The methodof claim 7, wherein the first computer comprises an integratedcard-based computer.
 9. The method of claim 3, wherein the secondcomputer comprises a logical partition in a logically-partitionedcomputer system.
 10. The method of claim 2, wherein forwarding thesecond network frame to the first network comprises passing the secondnetwork frame from the device driver for the second network adapter tothe device driver for the third network adapter, and transmitting thesecond network frame to the first network using the third networkadapter.
 11. The method of claim 2, wherein the first and third networkadapters are assigned the same MAC address.